Update CSS colour references to match image

Author: patrickhlauke

techniques/css/C41.html

@@ -35,13 +35,13 @@ <h4><abbr title="HyperText Markup Language">HTML</abbr></h4>
 					<h4>CSS</h4>                
 					<p>CSS to provide the indicator. It narrows the scope to buttons within the <code>main</code> element.</p>
 <pre><code class="language-css">button { 
-  background-color: #236AB8; /* medium-dark blue */
+  background-color: #003366; /* dark blue */
   color: white;
   padding: 10px;
 }
 
 main button:focus { 
-  outline: 3px #fff5be solid; /* light yellow */
+  outline: 3px #ffff00 solid; /* yellow */
   outline-offset: -4px;
 }</code></pre>
 				</section>